Climate change is expected to lead to increases in sea levels which could threaten the stability of rubble mound breakwaters in the future, as greater water depths will allow larger heights to reach the structures. Although this phenomenon is widely understood, the authors of the present chapter argue that an acceleration in the pace of sea level rise will require a more detailed assessment of risks and maintenance of breakwaters than at present, especially after 2050. This will alter port and breakwater design philosophy and lead to substantial increases in the cost to build and maintain these costly structures, especially in countries with relatively shallow coastal bathymetries such as Vietnam. The generic average increases in breakwater cross-sections were evaluated for four different rates of sea level rise showing that for the more extreme scenarios cases (for a sea level rise of 1.3 m over 50 years) a breakwater designed in 2050 could require between 8% (for the deeper sections) and 66% (for the shallower sections) more material than one designed in the 20th century not taking into account sea level rise. A case study of one such port, that of Phan Thiet in Vietnam, was used to showcase the problems involved.Climate change is expected to lead to increases in sea levels which could threaten the stability of rubble mound breakwaters in the future, as greater water depths will allow larger heights to reach the structures. Although this phenomenon is widely understood, the authors of the present chapter argue that an acceleration in the pace of sea level rise will require a more detailed assessment of risks and maintenance of breakwaters than at present, especially after 2050. This will alter port and breakwater design philosophy and lead to substantial increases in the cost to build and maintain these costly structures, especially in countries with relatively shallow coastal bathymetries such as Vietnam. The generic average increases in breakwater cross-sections were evaluated for four different rates of sea level rise showing that for the more extreme scenarios cases (for a sea level rise of 1.3 m over 50 years) a breakwater designed in 2050 could require between 8% (for the deeper sections) and 66% (for the shallower sections) more material than one designed in the 20th century not taking into account sea level rise. A case study of one such port, that of Phan Thiet in Vietnam, was used to showcase the problems involved.